Method of photolithographically defining three regions with one mask step and self aligned isolation structure formed thereby

a technology of three regions and masks, applied in the direction of photomechanical equipment, instruments, semiconductor/solid-state device details, etc., can solve the problems of reducing the efficiency of the fabrication line, adding processing steps, and almost impossible to line up the second mask exactly with the first, and achieves positive tone

Inactive Publication Date: 2000-11-14
IBM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method for defining three regions on a semiconductor substrate using a single masking step. The preferred embodiment uses a photoresist material having, simultaneously, both a positive tone and a negative tone response to exposure. This combination of materials can provide a new type of resist, which we call a hybrid resist. The hybrid resist comprises a positive tone component which acts at a first actinic energy level and a negative tone component which acts at a second actinic energy level, with the first and second actinic energy levels being separated by an intermediate range of actinic energy. When hybrid resist is exposed to actinic energy, areas of the resist which are subject to a full exposure cross link to form a negative tone line pattern, areas which are unexposed form remain photoactive and form a positive tone pattern, and areas which are exposed to intermediate amounts of radiation become soluble and wash away during development. This exposes a first region on the mask. By then blanket exposing the hybrid resist, the positive tone patterns become soluble and will wash away during development. This exposes a second region on the mask, with the third region still be covered by the hybrid resist. Thus, the preferred embodiment is able to define three regions using a single masking step, with no chance for overlay errors.

Problems solved by technology

First, the inherent complexity of adding additional processing steps reduces the efficiency of the fabrication line.
Secondly, it is almost impossible to line up the second mask exactly with the first.

Method used

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  • Method of photolithographically defining three regions with one mask step and self aligned isolation structure formed thereby
  • Method of photolithographically defining three regions with one mask step and self aligned isolation structure formed thereby
  • Method of photolithographically defining three regions with one mask step and self aligned isolation structure formed thereby

Examples

Experimental program
Comparison scheme
Effect test

example 2

This example illustrates the manner in which changing the type of photoacid generator and relative amounts of the various components can change the dissolution rate characteristics of the hybrid resist and subsequently the lithographic response. This second formulation was prepared and processed in a manner similar to EXAMPLE 1, however, it is comprised of the following components:

PHS with about 25% of the phenol groups protected with MOP, 90.8% of solids;

triphenyl sulfonium triflate, 1.3% of solids;

Powderlink, 7.8% of solids;

tetrabutyl ammonium hydroxide base, 0.1% of solids; and

sufficient PM acetate containing 350 ppm FC-430 surfactant as a solvent to form a 18.9% solids solution.

The dissolution rate characteristic of the resulting hybrid resist is shown in FIG. 14. The overall nature of the curve remains similar to that shown by the hybrid resist of EXAMPLE 1, in that the dissolution rate starts out low for an unexposed resist, increases to a high at about 5 mJ and decreases to a...

example 3

This example illustrates that the space width of the frequency doubled image can be changed by varying the protection level of PHS with MOP. Two different PHS lots having 24% and 15% MOP loading, respectively, were used to make hybrid formulations identical to that of EXAMPLE 1, except that the total solids contents were adjusted to 16.0% of the total to obtain film thicknesses of about 0.5 .mu.m. From these two stock formulations, several other formulations with average MOP levels ranging from 15 to 24% were prepared. Wafers were coated and soft baked at 110.degree. C., exposed on a MICPASCAN II DUV 0.5 NA stepper, post exposed baked at 110.degree. C. for 60 sec and finally developed with 0.14N TMAH developer. A reticle with an isolated chrome opening was printed in a hybrid resist film. The spacewidth of the resist image was measured and graphed as a function of the average MOP solubility inhibitor loading in the PHS used for making the respective formulations. It was found that t...

example 4

Negative tone imaging may be performed with the hybrid resist of the present invention, using a blanket DUV expose after the PEB and prior to the develop.

A hybrid resist formulation as described in EXAMPLE 2, above, was imagewise exposed with a chrome reticle with an electrical test pattern on a 0.5 NA DUV expose system. Silicon wafers (200 mm) with a 2000 Angstrom (.ANG.) film of polysilicon were used as a substrate so that the resulting etched patterns of the resist image could be measured with electrical probe techniques. After the post expose bake process, the wafers were cycled back into the expose tool (MICRASCAN II) and exposed at 10 mJ per square centimeter (cm.sup.2)with a clear glass reticle. A post expose bake process was not performed after the second exposure. The purpose of the second exposure was to remove the initially unexposed resist from the wafer, leaving only a negative tone resist pattern after develop.

The initial image-wise expose dose was 17-24 mJ / cm2, the po...

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Abstract

The preferred embodiment of the present invention provides a method for defining three regions on a semiconductor substrate using a single masking step. The preferred embodiment uses a photoresist material having, simultaneously, both a positive tone and a negative tone response to exposure. This combination of materials can provide a new type of resist, which we call a hybrid resist. The hybrid resist comprises a positive tone component which acts at a first actinic energy level and a negative tone component which acts at a second actinic energy level, with the first and second actinic energy levels being separated by an intermediate range of actinic energy. When hybrid resist is exposed to actinic energy, areas of the resist which are subject to a full exposure cross link to form a negative tone line pattern, areas which are unexposed form remain photoactive and form a positive tone pattern, and areas which are exposed to intermediate amounts of radiation become soluble and wash away during development. This exposes a first region on the mask. By then blanket exposing the hybrid resist, the positive tone patterns become soluble and will wash away during development. This exposes a second region on the mask, with the third region still be covered by the hybrid resist. Thus, the preferred embodiment is able to define three regions using a single masking step, with no chance for overlay errors.

Description

1. Technical FieldThe present invention relates generally to a process in the manufacturing of semiconductor devices. More, specifically, the present invention relates to a process for defining three regions on a semiconductor wafer with only one masking step.2. Background ArtPhotolithography has long been used to define and form semiconductor devices. Photolithography consists of depositing a photoactive resist on the semiconductor device and exposing the resist through a mask such that portions of the mask are exposed to radiation, and other portions are not exposed. If the resist was positive tone resist, then the portions of the resist which were exposed wash away during development. If the resist was a negative tone resist, then the portions of the resist which were not exposed during exposure wash away during development. Thus, conventional prior art is able to define two regions using a masking step, ie., the all the areas where resist is removed during development, and all o...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G03F1/14G03F7/095G03F7/20H01L21/027H01L21/02H01L21/762H01L21/70G03F1/00G03F7/004H01L21/302H01L21/3065H01L21/76
CPCG03F1/14G03F7/095H01L21/762G03F7/2024G03F7/70633H01L21/0274G03F7/2022G03F1/144
Inventor BRUCE, JAMES A.HOLMES, STEVEN J.LEIDY, ROBERT K.MLYNKO, WALTER E.SENGLE, EDWARD W.
Owner IBM CORP
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